Methods of making coated metal bodies and composite metal sheets



Nov. 27, 1962 TEMPERATURE 6" METHODS OF MAKING COATED METAL BODIES AND COMPOSITE METAL SHEETS Original Filed June 10, 1955 /2 PHASE ulna/m1 P POI/VT srsrm 0r STEEL IW-P ALLOY NH ALLOY IIVELY DIV/0E0 IVi-P ALLOY 23 SOL/0 SOL/0 24 I000 NICKEL 1V9 P $0LL/T/0/V 50L. E. I 900 ffff f a Z a E76? 23 25% PR/M4? NICKEL TEMP 250. gun-"(v15- much -L.-3". r 800 Y sau/r/on/ EUTECT/C i FEW? 22 1 i l E 25 Y 0 2 4 9 29 l0 l? 24 PHOSPHO/Pl/S /00 98 96 .94 92 .90 NICKEL.

0r STEEL Ni-P STEEL BASE METAL lVi-P M0) 5455 METAL 0r STEEL lVi-P ALLOY INVENTORS WILL/AM .T. CHE/MN WALTER E ALOUSE PAUL TALME Y m yu m States 3,965,535 METHODS F MAKENQ COATED METAL BODIES AND CUMPOSKTE METAL SHEETS William I. Crehan, Hinsdale, Waiter F. Klouse, Chicago, and Paul Talrney, Barrington, Elh, assignors to General American Transportation Corporation, (Ihicago, 111., a corporation of New York Ori inal application .iune 10, 1955, Ser. No. 514,472, now Patent No. 2,d8,568, dated Oct. 13, 1959. Divided and this application Aug. 16, 1557, Scr. No. 678,683

6 (Ilaims. (Cl. 29-484) The present invention relates to the method of making coated metal bodies and composite metal sheets, and more particularly to such bodies and composite sheets incorporating nickel-phosphorus alloy coatings. This application is a division of the copending application of William J. Crehan, Walter F. Klouse and Paul Talmey, Serial No. 514,472, filed June 10, 1955, now Patent No. 2,908,568, granted October 13, 1959.

It is an object of the invention to provide an improved method of coating a base metal body with a nickel-phosphorus alloy.

Another object of the invention is to provide an improved method of uniting two metal bodies that involves the step of fusing a nickel-phosphorus alloy layer therebetween and into wetting and bonding relation with the adjacent surfaces of the two metal bodies.

A further object of the invention is to provide a uniting method of the character described that is entirely operative even though one or both of the bodies are formed of a metal having a high chromium content.

A further object of the invention is to provide a method of wetting and bonding the surface of a chromium alloy, without melting the same, and without the utilization of an external flux, and involving only contacting the chromium alloy with a melt of nickel-phosphorus alloy.

A further object of the invention is to provide an improved method of making a composite metal sheet comprising two individual metal sheets united by an intermediate layer of nickel-phosphorus alloy.

A still further object of the invention is to provide an improved method of making a composite metal sheet comprising a base metal sheet clad with a chromium alloy sheet.

Further features of the invention pertain to the particular arrangement of the steps of the method; whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

FIGURE 1 is a phase diagram of the nickel-phosphorus system, as far as it is pertinent to the nickel-phosphorus alloys that are employed in the coatings and in the composite sheets of the present invention, and illustrating the mutual relationships among phase and temperature and composition in these nickel-phosphorus alloys;

FIG. 2 is an enlarged fragmentary sectional view of a composite metal sheet, that is made in accordance with the method of the present invention;

FIG. 2A is an enlarged fragmentary exploded sectional View of the elements of the composite sheet shown in FIG. 2, and illustrating a step involved in the method of making the same;

FIG. 2B is an enlarged fragmentary exploded sectional view of the elements of the composite sheet shown in FIG. 2, and illustrating modified steps involved in the method of making the same;

FIG. 3 is an enlarged fragmentary sectional view of a modified form of the composite metal sheet;

fire

FIG. 4 is an enlarged fragmentary sectional view of another modified form of the composite metal sheet; and

FIG. 5 is an enlarged fragmentary sectional view of a further modified form of the composite metal sheet.

At the outset, it is noted that in the operation of a continuous chemical nickel plating system of the character of that disclosed in US. Patent No. 2,658,839, granted on November 10, 1953 to Paul Talmey and William J. Crehan, there is employed a plating bath of the nickel cationhypophosphite anion type; and in the plating operation, nickel cations are reduced to metallic nickel and deposited upon the catalytic surface of the object undergoing the chemical nickel plating operation, and hypophosphite anions are correspondingly oxidized to phosphite anions and accumulate in the plating bath. In accordance with the method of Talmey and Crehan, the plating bath is continuously or periodically regenerated by the addition of nickel cations and hypophosphite ions, thereby to compensate the same for the depletion of these ions resulting from the plating reactions mentioned. Also, these plating reactions in the plating bath are productive of hydrogen ions, whereby hydroxyl ions are added in the regeneration to maintain the desired pH of the plating bath.

While this method greatly extends the useful life of the plating bath, it does not prevent the build-up of phosphite anions and alkali metal salts therein (assuming that the regeneration involves the addition of nickel sulfate, sodium hypophosphite and sodium hydroxide); whereby ultimately it is necessary to discard the plating bath, as a result of the build-up of high concentrations therein of phosphite anions, sulfate anions and sodium cations. Specifically, care must be exercised in this connection to prevent precipitation of nickel phosphite in the plating bath, since such precipitate serves as growth nuclei for the formation of metallic precipitate therein, with the resulting random decomposition of the plating bath. Specifically, the reactions involving the formation of the metallic precipitate in the plating bath are autocatalytic; whereby the formation of any substantial metallic precipitate therein effects the total decomposition of the plating bath very quickly and throughout the body thereof entirely at random and altogether independently of the catalytic surface of the body undergoing the plating operation.

Thus, a chemical nickel plating bath becomes spent when the phosphite anion concentration therein approaches the threshold of insolubility of nickel phosphite, and must be discarded, so as to prevent the possibility of random decomposition thereof in the plating system.

The spent chemical nickel plating bath contains valuable nickel, hypophosphite and phosphite, as well as sodium and sulfate; whereby it is ordinarily subjected to gross nickel salvage by treatment that induces random decomposition thereof, the residue of the plating bath comprising an aqueous liquid having the previously mentioned metallic precipitate suspended therein. The matter of the treatment of the chemical nickel plating bath to induce random decomposition thereof is exceedingly easy, as this phenomenon involves the previously mentioned reactions that are autocatalytic; whereby the reactions, once initiated, rapidly spread throughout the plating bath and proceed substantially on a quantitative basis with respect to the two ingredients (nickel cations and hypophosphite anions) with the formation therein of the metallic precipitate mentioned. Thus, all of the nickel cations in the plating bath are depleted in the presence of the norrna slight exce"s of hypophosphite anions; whereby the subsequent recovery of the metallic precipitate from the aqueous liquid effects the complete recovery of the nickel cations from the residue of the spent chemical nickel plating bath.

The initiation of the reactions mentioned is also exceedingly simple, as it is noted that a chemical nickel plating bath is normallyin a metastable state and issubject to spontaneous decomposition? Specifically, the

simplest procedure of initiating the reactions is to" seed chemical platingbath may, be initiated by appropriatelyinv creasingthe pHthereof, by raising the temperature thereof s i j to the boiling point, etc. Since the reactions are auto catalytic, as previouslynoted, it is very convenient, as a matter of manipulation, to initiate the same in a'small quantity ofthe spent chemical nickel plating bath oomtained in abeaker, or :the like, and then return, the con-L tents of the beaker into the vat ortank containing the bulk of the spent chemical nickel plating bath, thereby seeding thereactions in the bulk of the spent chemical nickel plating bath, in an obvious manner.

. "Heretofore, chemical nickel platersihave returned the metallic precipitate thus salvagedfr'om spent chemical.

nickel plating baths to initial nickel processors; whereby such processors, in turn, have recovered the nickel content of the metallic precipitate by smelting'operations, involvingreducing agents; whereby the crudem'etallic autocatalytic, and the character a natrixof nickelfin the resulting mass. As the temper-f i Theseconsiderationswillbe best understoodby reference to FIG lot the drawings; wherein there is illusgtrated aportion of the nickel-phosphorus system that is row range of permissible character.

of these first few nuclei ay depend entirely upon probability, within avery nar- Next, it has beendiscovered that when this metallic precipitate is heated to a temperature of about 406 C. an irreversible structural change Occurs therethrough in an exceedingly short time interval, whereby the phosphorus that was in solution in the nickel reacts with the nickel to produce nickel phosphide (Ni P), which latter compound; is dispersed in the form of: micro-crystals in meet this resulting mass is elevated, theNi P crystals grow in the nickel matrixuntil ultimately a melt is obtained in the temperature range 880 C. to 1100 C., depending upon composition; whereby the nickel and phosphorus constituents are in equilibrium. i 3 I pertinent to the nickel-phosphorus compositions, produced by the melting or the metallic precipitate noted; Specif: icaliypit was discoveredathat the eutectic composition 7 comprises nickel and phosphorus constituents containing 3 about 89% nickel'and 11% phosphorus by weight, and that the eutectic temperature is about 880 C. On the 1 curve 11, the melting point of nickel (1453 C.) is indinickel thus recovered has been refined by electrolytic operations for further use.

plating bath also contains substantial phosphorus," they have always treated this contained phosphorus as ?just another impurity encountered in the smelting of nickel ores; whereby the phosphorus contentof the metallic pre- 7 Although, these nickel proci 'essors have been informed of. the fact that the metallic precipitate thus salvaged from a spent chemical nickel cipitate has been totallywasted in these smelting opera-f Perhaps the primary reason for this gross salvage of only the nickel ingredient of this metallic precipitate by the nickel processors has been a total misconception of the fundamental character and composition thereof. Recently, this metallic precipitate has been discoveredto be cated at 12, and the eutectic point is indicated at 13., -Also, from'the curve 11,it will be observed thata composition containing about 5% phosphorus has a. melting pointof about 1150 C., a;c0mposition containing about 6% phosphorusihas a melting point of about 1100 (1.,

a composition containing, about 10% phosphorus has a r I melting point of about-950 C., and a composition cone "tainingabout 12% phosphorus has a melting point of V about 950: C.

The eutectic compositionof thesystemis not com-- pletely understood, since itappears that it involves fundamentally nickel and Ni P, and since the proportions by Weight are. not in strict accordance. with Dfaltons law;

an amorphous solidcomprising a metastable undercooled i solution of phosphorus in nickel, and having no specific a composition, but normally containing, as produced incident'to the random decomposition of a: chemical nickel plating bath of the nickel cation-hypophosphite anion, type, constituents comprising about 88 to 94% nickel and 6 to, 12% phosphorus by weight. The phosphorus coni tent is affected by the excess of'bothhypophosphite anions and phosphite anions in the spent chemical nickel plating bath, but only within the narrow range mentioned. Spe- I cifically, a high phosphite anion content, or a high hypophosphite anion content, in the spent chemical nickel plating bath insuresthatincident to random decomposition thereof the metallic precipitate produced will have. a high phosphorus content within this narrow range, but the 'hypophosphite anion content, in the spent chemical'nickel I plating bath is by'no means essential to the production of p a high phosphorus content in the metallic precipitate. i

Intact, the metallic precipitate produced incident tothe random decomposition of a pure simple Jfreshly prepared; standard aqueousv solution of nickel sulfate and sodium hypophosphite always contains phosphorus in the range 6 to 12% byweight, frequently has a phosphorus contentas high as- 11Q% by weighhand occasionally has a phophorus content-lets high as 12% by. weight. This i phenomenonis not really understood, astherandom decomposition of the same standard solutioriin two separate batches is. not necessarily productive of identical samples of metallic precipitate, as to phosphorus content. It is however, repeated and accurate analysis always yields this ratio of nickel and phosphorus by weight, and only.

nickel and Ni P have been detected in the alloy. I

All, of, the compositions that are produced by melting of the metallic precipitatenoted contain nickel and phos v phorus in the previously mentioned: range by weight" (about: 8 894% nickel undid-12% phosphorus); and

most of the, compositions fall in the even more limited range containing about 9093% nickel and 7 10% phosphorus by weight. Thus, it will be understood that when l the metallic precipitate is heated to a temperature sufficiently high to melt the same, a melt is produced in which the nickel and phosphorus constituents are in equilibrium about the curve 61 of the phase diagram of FIG. 1. Upon subsequent cooling, the melt becomes supersaturated with'nickel in"the e,vent the phosphorus t contentof thecompositioniis below 1.1%; whereas upon subsequent cooling, the melt becomes supersaturatediwith 1 iNi P in, the event'thephosphorus content of thefcom position is about 11%. Specifically, in the event there is a deficiency of phosphorus the melt becomes supersat .urated with nickel, uponsubsequent cooling; whereby solid n ckel is formed inthe solutionof the eutectic as the composition of the solution moves, downwardly. and" toward the right, along'the curve 61 and toward the suggested that the average character of the ultimately producedmetallic precipitate "may. be greatlyinfluenced by thecharacter of the first few nuclei'of the metallic precipitate that, form in the solution, sincethe reaction is eutectic point 65;. hence,- wherithe cooling ofthe melt oceeds tome eutectic temperature of about-1880 C, considerable,soIidnickelis presentin thesolution of, the i eutectic composition, sothat upon furtherlcooling of the v .mass, this solid nickelqis productive of primary nickel crystals in the mass ofthe eutectic. composition that appear as substantial nickel dendrites dispersed in the, fine crystals of nickel and Ni l comprising. the funda-- mental constitucntsof the eutectic composition Specifically, in the event there is anexcess ofphosphorus,

the melt becomes supersaturatedwith Ni P, upon subsequent cooling; whereby solid Ni P is formed in the solution of the eutectic as the composition of the solution moves downwardly and toward the left along the curve 61 and toward the eutectic point 63; hence, when the cooling of the melt proceeds to the eutectic temperature of about 880 C., considerable solid Ni P is present in the solution of the eutectic composition, so that upon further cooling of the mass, this solid Ni P is productive of primary Ni P crystals in the mass of the eutectic composition that appear as small crystals of Ni P dispersed in the fine crystals of nickel and Ni P comprising the fundamental constituents of the eutectic composition. Accordingly, it is the melting of the metallic precipitate noted, followed by the subsequent cooling and solidifying of the melt, that is productive of the nickel-phosphorus alloy characterized by the eutectic composition having dispersed therein the primary crystals mentioned. As previously noted, in this metallic precipitate, there is normally an excess of nickel in the composition, whereby the nickel-phosphorus alloys produced are normally characterized by the dispersion therein of nickel dendrites.

From a broad point of view, as a matter of definition, the original nickel-phosphorus material resulting directly from the nickel cation-hypophosphite anion reaction (the amorphous solid material described) may be termed an alloy, although it is not characterized by the eutectic composition noted; however, it is preferable to apply the term alloy to the final nickel-phosphorus material that results from the melting and subsequent solidifying of the original material mentioned, since this final material is characterized by the eutectic composition noted. Thus, hereinafter the term alloy will be used only to refer to this final material.

Now this nickel-phosphorus alloy is substantially different, as to characteristics and structure, from the solid nickel-phosphorus nickel that is chemically plated from a plating bath of the nickel cation-hypophosphite anion type and from the solid nickel-phosphorus material of the metallic precipitate. For examples, this nickel-phosphorus alloy is substantially magnetic, whereas the nickel-phosphorus plating and the metallic precipitate are substantially non-magnetic; and the specific resistance of this nickel-phosphorus alloy is considerably less than that of the nickel-phosphorus plating or the metallic precipitate. There are also many other physical and structural differences between this nickel-phosphorus alloy and the nickel-phosphorus plating and the metallic precipitate that are not here discussed at length in the interest of brevity.

Moreover, it will be understood that while the metallic precipitate must be melted to efiiect the production of the nickel-phosphorus alloy described above, it is not necessary to maintain the condition of the melt for any particular time interval.

The method of making the nickel-phosphorus alloy, described above, from the spent chemical nickel plating bath not only provides an efiicient scheme of salvaging valuable nickel and phosphorus therefrom, but provides an exceedingly valuable alloy having many important uses, as explained more fully hereinafter; and it is emphasized that the salvage method is applicable to a wide variety of chemical nickel plating baths, such, for example, as those disclosed in the following U.S. patents: No. 2,532,283, Brenner and Riddell; No. 2,658,841, Gutzeit and Krieg; and No. 2,658,842, Gutzeit and Ramirez. Thus, the chemical nickel plater may select the chemical nickel plating bath that is best suited to his particular operation, and subsequently subject the spent chemical nickel plating bath to salvage in accordance with the present method, and regardless of the particular composition of the chemical nickel plating bath.

A preferred chemical nickel plating bath of extremely wide utility is disclosed in the copending application of Gregoire Gutzeit, Paul Talmey and Warren G. Lee, Serial No. 479,088, filed December 31, 1954, now Patent No.

2,822,293, granted February 4, 1958, this particular plating bath being admirably suited to the continuous plating process disclosed in the Talmey and Crehan patent. The chemical plating bath of the Gutzeit, Talmey and Lee application mentioned essentially comprises an aqueous solution of a nickel salt, a hypophosphite, a complexing agent selected from the group consisting of lactic acid and salts thereof, and an exalting additive selected from the group consisting of propionic acid and salts thereof. In this plating bath, the absolute concentration of hypophosphite is within the range 0.15 to 1.20 moles/liter, the ratio between nickel ions and hypophosphite ions is within the range 0.25 to 1.60, the absolute concentration of lactic ions is within the range 0.25 to 0.60 mole/liter, the absolute concentration of propionic ions is within the range 0.025 to 0.060 mole/liter, and the pH is within the approximate range 4.0 to 5.6.

This particular chemical nickel plating bath is most satisfactory in carrying out a wide variety of nickel plating operations; and, of course, when it becomes spent, it may be subjected to the present salvage method to produce the nickel-phosphorus alloy previously described.

It has also been discovered that the stray plating that may occur in an undesirable manner in a chemical nickel plating system of the character of that of the T almey and Crehan patent may also be employed in the production of the nickel-phosphorus alloy described in the general manner disclosed above. In other Words, this stray plating that accumulates in the bottom of the tank in which the chemical nickel plating bath is stored, in the filters of the system, etc., may be accumulated and melted in the manner described above, either alone or with the metallic precipitate mentioned, in order to produce the nickel-phosphorus alloy described. In fact, it has recently been discovered that this stray plating is also an amorphous solid comprising a metastable undercooled solution of phosphorus in nickel, and having no specific composition, but normally containing, as produced, constituents comprising about 88 to 94% nickel and 6 to 12% phosphorus by Weight. Since the metallic precipitate mentioned and the stray plating mentioned are substantially identical, as a matter of composition, they may be melted together in order to produce the nickel-phosphorus alloy described.

As a matter of convenience in handling, the molten nickel-phosphorus alloy described may be cast into rods, bars, or other commercial forms, for subsequent use; whereby, such forms of the alloy, Within themselves, comprise useful articles of convenience.

This method of making the nickel-phosphorus alloy is disclosed and claimed in the previously mentioned application of Crehan, (louse and Talmey, Serial No. 514,472, filed June 10, 1955, now Patent No. 2,908,568.

Turning now to the utility of the nickel-phosphorus alloy that is produced by the present method, it is first noted that in a molten condition, it has very pronounced wetting and bonding characteristics; whereby it is generally useful as a coating material, and may be readily applied in a great variety of ways to a vast array of different base metal bodies after they have been subjected to standard degreasing, cleaning and pickling operations. Specifically, such an alloy coating may be applied to the cleaned surface of a base metal body by any one of the following groups of steps, in accordance with the present method:

(1) The cleaned base metal body is heated, and the alloy in molten condition is poured over the hot body in order to apply a cast coating of the alloy upon the body.

(2) The cleaned base metal body, at ambient temperature, is immersed in a molten mass of the alloy, and subsequently withdrawn with respect thereto, in order to apply a hot-dipped coating of the alloy upon the body.

(3) A mass of the alloy, at ambient temperature and in finely divided form, is sprinkled upon the cleaned surface of the base metal body, the body having been preing of the alloy upon the body.

coating of the alloy upon the body.

(5) A portion of a bar of the alloy ismelted with a torch, or the lil e,.onto the heated and cleaned surface viously heated to 'a high temperature, in orden to apply a melted coating of the alloy upon the body.

of the base metal body, in -order to apply a tinned-coat (6) A mass of the metallicprecipitate," or the r stra y plating in finely divided form, is sprinkledrupon the cleaned'surface of thebase metal body, the easy having" been previously heated to a high*temperature,"in order to meltthe mass, wherebyupon subsequent cooling and solidifying of the melt, the alloy coating is formed in situ,

upon the :lbOdY. i a i p (7) A mass of the metallic precipitate, or the stray plating in finely divided form, is placed upon the cleaned 7 surface of the base metal-body,"at ambient temperature,

and the body and the carriedxmass are transferred to a1 furnace or oven and heated in order to melt the mass,

7 whereby upon subsequent cooling and solidfying of the melt, the alloy coating is formed in situ upon the body.

(8) A portion of a'ba-r of the compressed/metallic precipitate, or the stray plating, is melted with atorch; or the like, ontothe heated and cleaned surface of'the base metal body; whereby upon subsequent cooling and" solidifyinggof the melt, the alloy' coating is formed in si-tu upon the body. I

The foregoing suggestions are merely illustrative of the many ways in which the previously prepared alloy may be applied as a coating upon a'body'and in which the alloy may be made in situ from the melted metallic precipitate, or the strap plating, applied as acoating upon a body; and many othermodes of producing such coatings will be immediately apparent to those, skilled in the tinning, soldering, brazing, galvanizing and other metal-I coating arts. i

Turning now to the character of the base metal of the body that may be coated with this alloy, it is noted that. the only limitation that has been discovered is that it must have a melting point sufficiently high that it is not appreciably melted in contact with the molten alloyat a temperature in the general range 880 C. to, 1100" C., as themolten alloy must be heated to a temperatureqin this general range toobtain the desired liquid condition thereof. Also, the alloy in molten condition must wet metal, but this condition does not comprise'a substantial limitation, as the wetting andbondingcharacteristics of and bond with repect to the cleaned surface of the base 1 lphos'phite anion typerthc surface of thebase metal must".

becatalytic tcvthe plating reactions involved, so as to bring aboutthe chemical reductionist the nickel cations and {the deposition of i the resulting metallic nickel, "and the companion oxidation of hypophosphite anions to" phosphite anions; all as previously explained in the Talrney and "Crehan' patent However, in accordance with the present method, the nickehphosphorusalloyhas been previously produced, or is produced in situlincident i to the cooling and solidifying-of the melted metallic g precipitate; or the stray plating; whereby it isnot critical that the cle'anedsurface of thebasehmetal be catalytic Y in order toobtain a coating thereon with the previously producedalloy, orthe alloy thus produced: in situ.

Referring now to 2 of the drawings, there isillustrated a composite metal sheet 21,- .embodying thefeatures of the present invention, and comprising an in,-

termediatesheet 22 formed of base -metal,-= two outside sheets ZItjand 24 formedof chrome-steel.- and twounit Minglayers 25a and 25b formed or HlGkBLPhOSPhOIjIlS alloy, the. alloy layer 25:: being disposed between and intimately bonded to" the adjacent surfaces of the sheets 22 and'23, and the layer-25b being disposed'between and p intimately bonded to-the adjacent surfaces at the sheets a and 2a."

The nickel-phosphorus alloy'of thela'ye'r s 25a and 25b contents. about fito 94%. nicltel and 6"tc 12 pbos f phorusby weight and comprises the eutectic composh tion rnentioned including nickel and, phosphorus constite,

uents containing about 89% nickel and 11% phosphorus bybweight; and, having an eutectie temperature of about 880 C. Since the alloy ordinarily contains excess nickel with rcspect to the eutectic composition thereof,

ordinarily, it has .amelting point somewhatabout the eutectic temperature and disposed in: the approximate range'880" C. to llO0 C., depending uponthe composition thereof. More particularly, this alloy is thatlwhich is automatically produced by the melting of themetallic f precipitate, or bythe melting'otthe stray'plating, followed by cooling and solidifying of the melt, as pre viously described.

Turning now to the method of making the composite. metal sheet 21, in accordance with the present inven- I tion, and referring to FIG. 2A, it is noted that all of the surfaces of theindividual sheets 22:, 23' and 24 are first thoroughly degreased, cleaned and lightly pickledin a suitable acid, such as hydrochloric acid; and then the alloy coating 25' is applied to the cleaned exterior surfaces of the sheet22 in any suitable manner and as pre? viously described; The alloy coating 25'- is intimately" bonded to the surfacesof the intermediate sheet 22 and comprises the two face portions 254; and25b respectively carried by the two. faces of the intermediate sheet 22 thereby. These peculiar wetting and bonding char'ac teristics of the moltenalloy are believed to flow. from the circumstance that the phosphorusconstituents of the melt are capable of reducing chromic oxide, as wellas of a great variety of bodies formed of base metals, precious metals, or alloys thereof; which coatings are. useful either as final protective coatings-for the bodies thus coated or as uniting layers employed in securing such. bodies to still other such bodies.

As a matter of fact, the present method removes a limitation with respect tothe conventional chemical nickel and the ,two' edgeuportions 25c respectively carried by the two edges of the intermediate sheet 22. r

For exatnple, the alloy coating- 25v may be applied to the cleaned surfaces of the basemc'tal sheet 22 by a hot dipping step and involving the immersion of the sheet'ZZ for a suitable time interval in a molten 'mass .ofthealloy. t l I.

Next, the sheets 22,23 and 24' are stacked so that l the face portionsflZSa and 25b of the layer 2 5v are dis-l posed in respective engagements with the adjacent cleaned, face surfacesfofjthe outer sheetsZB. and 241 The edges.

f of .tlie,sl1eets-22,2 3 and .24 may be tack-welded, if

v desiredin an 'obviousma'nner, .not; shown, in order to secure together the assembly, prior to fusion of' the lay 25, and in order to facilitate handling ofthe assembly,

plating process and concerning'the catalytic character of p the base metal. More particularly, in order to obtain plating upon the cleaned surface of a basemetal' from a chemical nickel plating bath of the nickel, cation'hE/Pm Theuthe'assetnbly is subiected to heat and pressure in order toeifectselective'fusion .ofthe'layer 25; whereby the face portions ZSaandZSb thereof-respectivelyprm M duce correspondingmelts, that are forced-,into wettingf tbonding relatiori' with the respective cleaned face surfaces ofthe outer sheets 23 and 24' in contact therewith, and also into wetting and bonding relation with the 9 respective face Surfaces of the intermediate 'sheet 22, in order to unite the assembly;

The assembly may be heated to effect the selective melting of the layer 25 in a furnace or oven; and it is preferable that the oven contain an inert atmosphere, such as nitrogen, as the assembly must be heated to a temperature in the approximate range 880 C. to llOO C., in order to melt the layer 25, the melting point of this nickel-phosphorus alloy being in this general range and being variable depending upon the composition thereof. As previously explained, the required pressure may be effected upon the assembly in any suitable manner. For example, the assembly may be transferred from the oven upon melting of the layer 25', to a suitable press; whereby the assembly is retained under pressure until the melts cool and solidify, uniting the individual sheets 22, 23 and 24.

Alternatively, when the sheets 22, 23 and 24 are relatively narrow, so that they comprise what may be termed strips, the heating and pressing Steps may be conveniently combined in a Single step by utilizing an electric resistance welding machine of the conventional roller-electrode type. In this operation, the assembly is passing between the two opposed roller-electrodes of the welding machine, so that the required pressure is exerted therebetween upon the stack of the individual sheets of the assembly; and simultaneously a substantial electric current is passed between the two roller-electrodes and through the assembly, so that the required heating of the face portions 25a and 25b of the layer 25 is effected. This combined step is well-suited to the method, since the face portions 25a and 25b of the layer 25 each has a high specific electrical resistance with respect to that of any one of the individual sheets 22, 23 and 24, so that the electric heating is preferentially concentrated in the face portions 25a and 25b of the layer 25.

After cooling of the assembly, the edges thereof are trimmed to remove the surplus alloy, etc., thereby producing the finished composite metal sheet 21, as shown in FIG. 2.

In the foregoing description of the composite metal sheet 21, and the method of making the same, it has been assumed that the individual elements 22, 23 and 24 are sheets of the required thickness to produce the finished composite sheet 21 of the required structure upon the uniting of the individual elements 22, 23 and 24; however, this preferred form of the method is not essential thereto, as the individual elements 22, 23 and 24 may be of such thickness that they comprise slabs, so that the united assembly comprises a billet. In this case, the billet thus produced may be subjected to subsequent working operations, such as hot or cold rolling, forging, etc., to produce the composite metal sheet 21 of the required thickness. For example, in the finished structure 21 of FIG. 2, the total thickness may be 250-mils, the element 22 having a thickness of ZOO-mils, and each of the elements 23 and 24 having a thickness of 25-mils.

In the foregoing description of the method of making the composite metal sheet 21, it was assumed that the continuous coating 25 of nickel-phosphorus alloy was first applied to the intermediate sheet 22 before the stacking of the individual sheets 22, 23 and 24 in order to produce the assembly to be subsequently worked to effect the uniting thereof; all as described in conjunction with FIG. 2A. However, as an alternative method, the individual sheets 22, 23 and 24 may be stacked with the alloy of the metallic precipitate or the stray plating layers 25a and 2512 respectively carried by the individual sheets 22 and 24 in producing the assembly, and before further working to efiect uniting. In this regard, the layer 2512 may be first placed upon the cleaned upper face of the outside sheet 24 in the form of the metallic precipitate, or the stray plating in finely divided form,

containing the nickel and phosphorus constituents, and before the production of the nickel-phosphorus alloy. Then the intermediate sheet 22 may be stacked upon the layer 2511, with the lower cleaned surface thereof in direct contact therewith. Then the layer a of previously produced nickel-phosphorus alloy in finely divided form may be placed upon the cleaned upper face of the intermediate sheet 22; and then the outer sheet 23 may be stacked upon the layer 25a with the lower cleaned surface thereof in direct contact therewith. Finally, the edges of the sheets 22, 23 and 24 may be suitably secured together in order to retain the assembly in place preceding further working.

In this case, when the assembly is subjected to heat and pressure, in the manner previously explained, the layer 25a of finely divided nickel-phosphorus alloy produces a corresponding melt, while the layers 25b of metallic precipitate, or stray plating in finely divided form, produces a corresponding melt and is converted into the nickel-phosphorus alloy upon cooling and solidifying, in the manner previously explained. This alternative procedure within itself comprises alternative procedures, as it is apparent that the layer disposed between each two. of the sheets 22, 23 and 24- may comprise either the previously produced nickel-phosphorus alloy in finely divided form or the metallic precipitate, or the stray plating in finely divided form. Accordingly, it will be understood that in the event the layer disposed between two of the sheets comprises nickel-phosphorus alloy in finely divided form, only melting of the previously produced alloy is involved. On the other hand, in the event the layer disposed between two of the sheets comprises the metallic precipitate, or the stray plating in finely divided form, both melting and alloying of the nickel and phosphorus constituents are involved. However, in any case, the ultimate result is the same that there is provided a uniting layer of nickel-phosphorus alloy between the two sheets.

Also, in the foregoing description of the composite metal sheet 21, and the method of making the same, it has been assumed that it is desirable to produce a structure in which both sides of a base metal sheet are cladded by chrome-steel sheets; however, this structure of the composite metal sheet 21, as shown in FIG. 2, is unusual and was selected only for the purpose of illustrating the broad application of the present method. More particularly, it is ordinarily necessary to elfect cladding of only one side of a base metal sheet; whereby the composite metal sheet 31 of FIG. 3 comprises the common form of the structure embodying the present invention. Specifically, the composite metal sheet 31 comprises a base metal sheet 34, a chrome-steel sheet 33, and an intermediate uniting layer of nickel-phosphorus alloy 35a.

The method of making the composite metal sheet 31 is the same as that described in the making of the composite metal sheet 21 and is not repeated in the interest of brevity.

Referring now to FIG. 4, another modified form of the composite metal sheet 41 is illustrated that comprises two identical base metal sheets 43 and 44 and an intermediate uniting layer 45a of nickel-phosphorus alloy; and referring to FIG. 5, a further modified form of the composite metal sheet 51 is illustrated that comprises two identical chrome-steel sheets 53 and 54, and an intermediate uniting layer 55a of nickelphosphorns alloy. The composite metal sheets 41 and 51 are also made in accordance with the present method, as described above, in the making of the composite metal sheets 21 and 31; whereby it will be understood that the composite metal sheets and methods of the present invention are by no means limited to structures involving a base metal sheet that is cladded with a chrome-steel sheet. The important point in this regard resides in the fact that the present method is applicable to the making of such 21, 31, 4l andt5l, the metalof at composite metal sheets involving one ormore sheets orm formed of metals containing substantial chromium, in

view, of the usual interference of the chromium withwet, l tingand bonding by the formation of chromic oxide upon the surface of the sheetcontaining any'substantialamount of chromium These melting andbondingcharacteristics;

of the nickebphosphorus ally are, by nomeans, peculiar to chromium, but aregeneral characteristics; whereby a 7, sheet in the-formation therefrom of ultimate articles of j manufacture. v

aluminum and its alloys are readily wet and bonded by. i

the melt, notwithstanding the usual aluminum oxides on the surface of such aluminum alloy sheets;

Reconsidering the presentmethod, 't is pointed out that the nickebphosphorus alloy comprising the uniting layer between the two metal sheets may have been previously produced by" themelting of; the metallic precipitate rccov ered from a chemical plating bath of the nickel-cationhypophosphiteanion type following random decompose tion thereof, or alternatively thenickel-phosphorus alloy vid'ual sheets unite d bythe corresponding one or more v nickel-phosphorus layers isvery advantageous in view of the tactthat thej two or more lnd ii'ldllfdlillftelal sheets i thereof are securely united and subject to noseparation or relativejmovernents; incident to subsequent working (rolling, drawing, cutting, etc.) j of the co-rnposite 'rnetal Whilet here has been'descriliediwhatis at presentcon sideredtoibe the preferred-embodiment of theinvention, it will be understood that various modifications may be made theeein, and it is; intended to cover in the appended comprising the 'unitinglayer between the twornetal sheets I may be produced in situby themeiting of the metallic incident to the uniting of the two metal sheets.

Q20 precipitate mentioned, or the stray plating mentioned,and i 'As previously explained, there is no particular or criti-1 cal limitation with regard to the composition of the metal of anyone of the individual metal sheets involved in; the:

composite metalsheet; however,fas a practical matter, in y the productionof such composite metal sheets the most,

important industrial metals comprise: iron and its alloys, cobalt and its alloys, nickel and its alloys,;copper and its a1loys,silver and its alloys goldand its alloys, palladium and its alloys and platinumand its alloys, I 7

For example in each of the compositemetal sheets i vidual sheets incorporated therein will ordinarily com-H prise one of the following elements' or alloys: iron,

carbon-steel, chrome steel, cobalt-steel, silicon-steel, manganese-steel, nickel-steel, molybdenum-steel, nickel-cobalt least one of the indio steel, nickel-chronic-stoel, chrome-mangztnese-steel, mam

ganesemolybdenum steel, chrome-coppermickebsteel, copper, brass, bronze, silicon-bronze, Phosphor-bronze, beryllium-copper," cadmium-copper, chromium-copper, nickel-copper,

aluminum, aluminum-brass, aluminum said metal body, applying saidwfinely divided mass of b metallic 1 precipitate to the cleaned surface of said metaly bronze, silver, palladium-silver, nickel-silver, coppersilver, zinc copper silver, zinc-cadmium-copp'er-silVer, gold, coppergold, copper-allyer-platinum-gold, copper silver-palladium-gold, platinum;

gold-platinum, silveri platinum, iridium-platinum, rhodium-platinum, palladium,-

claims all such modifications as fall withinthe true spirit and scope of the invention.

Whatisclaimedis: t

l. The method of coating a metal body; which method comprises providinga recovered mass of metallic preci pirate produced by decompositionof a-fspent? chemical;

nickel plating bath containingnickel cations and hypophosphite anions and phosphite'anions and comprising about 88 to 94% nick eland.about 6 to 12% phosphorus by weight, heating said mass of metallic precipitateto produce a melt therefrom, cleaning the surface of said? 3 metal body,fcontacting the'cleaned surface of said metal body, with said meltinflorder toprovide alayer of said and bondingtrelation therewith, whereby,

melt inwetting upcngsubsequent cooling and solidifying of said melt a 2. The method of coating a metal body; which method comprises providing in finelydivided form a recovered; :fi mass of metallic precipitate produced by decomposition of a spent, chemical nickel plating bath containing nickelcations and hypophosphite anions: and phosphitc anions and comprising about-88 to 94% nickel and about 6 to 12% phosphorus by weight, cleaning the surface of body, and heating said metal body and said mass of finely divided metallic precipitate at a temperature below the platinum, tungstenplatinum, nickel-platinum, rutheniumplatinum, gold-silver-platinum, palladiumgold-platinum nickel, chromiumr palladium, coppengold palladium, nickel, and cobalt; i

Thus, the cladding arrangement is of exceedingly wide utility, embracing the cladding'of base metals Wl'th the full range of stainless steels, with silver (of the general character of Sheineld'plate), etc. i

IIl VlBW of the foregoing, it is apparent that there has i been provided an improved method of coating base metal,

bodies with anickel phosphorus alloy, as well as an improved article of manufacture comprising such coated metal bodies. Furthenthere has been provided" an improved method of making a compoisite metal sheet that involves two individual metal sheets and aniritermedi'ate uniting layer of nickel-phosphorus alloy, wherein the alloy 2 layer possesses outstandingwetting and bondingcharacteristics permitting the union of the two individual metal sheets when they areformed of a great varietyof metals.

The metal body provided with the coatingoftniclrelmelting point of saidcmetal body and above the melting point of said mass of means precipitate in order selec- @tiveiy to meltnsaid mass-of nietallictpreeipitate and to flow a layer of the resulting melt intowetting and bonding relation with the cleaned surface of said metal body,

whereby upon subsequent cooling and solidifyingot said f melt a, nickel-phosphorus alloy coating is provided, that is intimately bondcd to said cleaned surface of said metal body, said alloy being characterized by'an eutectic cornposition comprising constituents containing about 89% j nickel and 11% phospliorus .by'weightrand having'an eutectictemperature of about 880C. I i j bodies; which 2 method comprises providing'a recovered mass'of metallic precipitate, produced'by decomposition of a spent? chemical: nickel plating bath: containing" nickel cations and hypophosphite anions and'pho'sphite anions and com I prising about 88 to 94% .nicke1 and aboutb to 12% phosphorus by Weight, heating said mass of metallic 3. The method of uniting two metal precipitate to produce a" melt therefrom, cleaniilg, two

surfaces respectively provided on said two bodies, ar

rangingsai-d two bodies anda layer of said melt so that phosphorus alloy is very advantageous in view of the facts that the coating is tenaciously honded to the surface of the metal body and subject to no blistering, peeling or spelling in use, and is characterized by adhesion, wear resistance and resistance to corrosive attack by'ord nary acids, bases and other reagents comparable n tact, superior) to'electrodepositednickel. Moreover, the

' composite metal sheet including the two or more indisaidtwo cleanedsurface's" are disposed in adjacent facing spaced-apart relation Withsaid layer of said melt therebetween in wetting andlbonding relation'therewith, wherelay-upon subsequent cooling and solidifying of said melt a nickeLphosphorus alloy coating is providedithat is intimately bonded to said cleaned gsurfaces of said; metal bodies securely uniting said two metal bodies, said alloy being characterized by an eutecticcomposition comprising constituents containing about 89% nickel and 11% phosphorus by weight and having an eutectic temperature of about 880 C.

4. The method set forth in claim 3, wherein the metal of at least one of said two metal bodies contains sufficient chromium substantially to interfere with ready wetting and bonding.

5. The method of making a composite metal sheet including two individual sheets and an intermediate uniting layer of nickel-phosphorus alloy; which method comprises providing a recovered mass of metallic precipitate produced by decomposition of a spent chemical nickel plating bath containing nickel cations and hypophosphite anions and phosphite anions and comprising about 88 to 94% nickel and about 6 to 12% phosphorus by weight and having a melting point well below that of the metal of either of said two individual sheets, cleaning two surfaces respectively provided on said two individual sheets, applying a layer of said mass of metallic precipitate to at least one of said two cleaned surfaces, stacking said two individual sheets so that said two cleaned surfaces are disposed in adjacent facing spaced-apart relation with said mass of metallic precipitate therebetween and in contact therewith, and subjecting said stack to heat and pressure so as selectively to melt said mass of metallic precipitate and to flow the resulting melt into wetting and bonding relation mutually with said two adjacent cleaned surfaces in contact therewith, whereby upon subsequent cooling and solidifying of said melt a nickel-phosphorus References Cited in the file of this patent UNITED STATES PATENTS 2,232,176 Guthrie Feb. 18, 1941 2,397,400 Barwick Mar. 26, 1946 2,795,040 Antel et al June 11, 1957 2,798,843 Slomin et a1. July 9, 1957 2,908,568 Crehan et al Oct. 13, 1959 FOREIGN PATENTS 487,263 Great Britain June 17, 1938 OTHER REFERENCES Journal of Research of the National Bureau of Standards, November 1947, vol. 39, No. 5, pages 385-395. Copy in Scientific Library.

Scholder et al.: Zeitschreft fur Anorganische und Allgemeine Chemie, vol. 198, No. 4, pages 329-351 (1931). Copy in Scientific Library. 

1. THE METHOD OF COATING A METAL BODY; WHICH METHOD COMPRISING PROVIDING A RECOVERED MASS OF METALLIC PRECIPITATE PRODUCED BY DECOMPOSITION OF A "SPENT"CHEMICAL NICKEL PLATING BATH CONTAINING NICKEL CATIONS AND HYPOPHOSPHITE ANIONS AND PHOSPHITE ANIONS AND COMPRISING ABOUT 88 TO 94% NICKEL AND ABOUT 6 TO 12% PHOSPHORUS BY WEIGHT, HEATING SAID MASS OF METALLIC PRECIPITATE TO PRODUCE A MELT THEREFROM, CLEANING THE SURFACE OF SAID
 3. THE METHOD OF UNITING TWO METAL BODIES; WITH METHOD COMPRISES PROVIDING A RECOVERED MASS OF METALLIC PRECIPITATE PRODUCED BY DECOMPOSITION OF A "SPENT" CHEMICAL NICKEL PLATING BATH CONTAINING NICKEL CATIONS AND HYPOPHOSPHITE ANIONS AND PHOSPHITE ANIONS AND COMPRISING ABOUT 88 TO 94% NICKEL AND ABOUT 6 TO 12% PHOSPHORUS BY WEIGHT, HEATING SAID MASS OF METALLIC PRECIPITATE TO PRODUCE A MELT THEREFROM, CLEANING TWO SURFACES RESPECTIVELY PROVIDED ON SAID TWO BODIES, ARRANGING SAID TWO BODIES AND A LAYER OF SAID MELT SO THAT SAID TWO CLEANED SURFACES ARE DISPOSED IN ADJACENT FACING SPACED-APART RELATION WITH SAID LAYER OF SAID MELT THEREBETWEEN IN WETTING AND BONDING RELATION THEREWITH, WHEREBY UPON SUBSEQUENT COOLING AND SOLDIDFYING OF SAID METAL A NICKEL-PHOSPHORUS ALLOY COATING IS PROVIDED THAT IS INTIMATELY BONDED TO SAID CLEANED SURFACES OF SAID METAL BODIES SECURELY UNITIND SAID TWO METAL BODIES, SAID ALLOY BEIGN CHARACTERIZED BY AN EUTECTIC COMPOSITION COMPRISING CONSTITUENTS CONTAINING ABOUT 89% NICKEL AND 11% PHOSPHORUS BY WEIGHT AND HAVING AN EUTECTIC TEMPERATURE OF ABOUT 880*C. 